The present invention relates to an improvement to molds such as that disclosed in U.S. Pat. No. 4,508,309 issued to Robert A. Brown, and U.S. Pat. No. 5,795,529 issued to Walter L. Reid, Jr., all of which were assigned to Acushnet Company and are incorporated herein by reference. The patents disclosed in prior art mold frames typically contain a plurality of cavities therein, which accommodate golf ball half-molds and are disposed in a closely packed arrangement.
Mold cavities are use to manufacture the dimpled cover portions of golf balls. The shapes, dimensions, and pattern of the dimples significantly contribute to aerodynamic performance of the ball as shown by wind tunnel testing and performance testing using robots and golfers. Achieving the desired aerodynamic performance properties requires the ability to produce such dimensions and shapes consistently. Because a golf ball receives its dimples from a molded cavity, the integrity and characteristics of the dimples formed on the golf ball are dependent upon the accuracy of the mold cavity from which the dimples are formed.
Typical compression mold frames generally include a plurality of bores and channels which penetrate through respective rows of cavities, and are fed by utility inlet lines for receiving a thermal medium such as steam or cooling fluid. Inlet lines are typically disposed at one end of a bore and an outlet is disposed at the end of the bore at an opposite side of the mold frame. The mold frame includes cross bores on opposite ends of the cavity rows for providing fluid communication between the bores. The ends of each bore and cross-bore, except for the inlets and the outlets, may be plugged to selectively block the cross-bores to create a serpentine series flow of the thermal medium through the adjacent cavities. The prior art discloses a variety of flow patterns for the cooling and heating mediums.
Whatever the flow characteristics of the particular mold frame, the cavities of prior art mold frames periodically need to be replaced, due to wear or breakage. Because of the construction and placement of the O-rings, it is necessary to remove the entire mold frame which includes disconnection all the utility lines entering and exiting the frame. This creates a significant production downtime.
When a golf ball is made using a molding process such as compression molding, two oppositely facing mold halves are used, an upper mold half and a lower mold half, with each mold half having a hemispherical, inversely dimpled mold cavity formed out of metal. Each mold half is approximately one half of the size of a finished ball. It is an industry standard to make inversely dimpled mold cavities out of metal, typically brass. A metal like brass is chosen primarily because of durability, mechanical strength, efficient thermal transfer, and ability to withstand higher pressures and temperatures without deforming. When the two mold halves are put together form an internal cavity that is generally spherical with an internal cavity that is generally spherical with an inversely dimpled pattern representing the negative image of the dimple pattern that will be produced on the golf ball formed therein.
Traditionally, in the multi-cavity compression molding of a golf ball cover or inner layer, each mold cavity is fitted with a pair of O-rings, one on each side of the utility to allow faster heating and cooling of the cavities to prevent leakage out of the mold surfaces. As previously stated, this O-ring(s) concept makes quick changing of cavities for the product changeover (dimple changes) or replacement of one or more damaged cavities very difficult. The most common reason for changing out a cavity is because of insufficient mold release which causes the product to stick.
The second most significant reason for needing quick changing cavities is that the cavities must be periodically treated with a release agent to enable the easy release of the golf ball product from the cavity. These release agents are of two types. The first type is a more permanent release agent which needs to be baked-on and requires baking temperatures in the 600° F. to 750° F. range. This release agent is more effective and doesn't transfer to the product. Since the O-rings are mounted on the side of the mold, and since they cannot sustain these high temperatures, the complete disassembly of all the mold cavities and removal of all O-rings is required to apply a permanent baked-on release agent. Because the production downtime caused by shutting down the hydraulic press, disconnecting the utilities to the frame, and removing the entire frame to apply the permanent release agent has been such an inconvenience, a second type of release agent has become popular and is widely used. This second type of release agent is sprayed on at the reduced temperature of between 250° F. to 350° F. which will not damage the O-rings. While this semi-permanent (sacrificial) release agent may be convenient, the procedure must be repeated often (some times every hour) and it allows the transfer some of the agent to the molded ball thereby causing significant adhesion related problems during finishing operations such as printing or painting. There is a real need for using the permanent baked-on release agent without shutting the entire operation down to change out the mold frame.
The present invention provides for a mold cavity that allows a quick changeover of the cavities, and also allows for an easy method of applying a baked-on mold release without having to remove the mold frame from the press.